Eight crystalline phases of bismuth vanadate by controllable hydrothermal synthesis exhibiting visible-light-driven photocatalytic activity

Abstract

• We successfully prepared eight crystalline phases of bismuth vanadate by applying the hydrothermal method. • m -BiVO 4 exhibits the greatest visible-light-driven photocatalytic activity on the CV of a series bismuth vanadate. • In the degradation reaction, O 2 − was the major active species, whereas OH and h + were the minor ones. • E g were 2.0–2.3, 2.1–2.2, 2.1–2.3, 2.1–2.2, 2.3–2.5, 2.6, and 2.2–2.6 eV for eight bismuth vanadate, respectively. By applying the hydrothermal method, we successfully prepared bismuth vanadate in a series of crystalline phases. The characteristics of the samples were identified using various techniques, such as scanning electron microscopy–energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, high-resolution X-ray photoelectron spectroscopy, diffuse reflectance ultraviolet–visible (UV–vis) spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis. Consequently, a BiVO 4 series, including monoclinic BiVO 4 ( m -BiVO 4 ), tetragonal BiVO 4 ( t -BiVO 4 ), BiV 1.025 O 4+X , Bi 4 V 2 O 11 , Bi 14 V 5 O 33 , Bi 12 V 2 O 23 , and Bi 9 VO 16 , were effectively prepared using a simple solution-based hydrothermal method. The powder suspension’s photocatalytic activity and the solution’s crystal violet (CV) concentration were measured through UV–vis spectroscopy. The UV–vis spectra revealed optical band gaps of 2.0–2.3, 2.1–2.2, 2.1–2.3, 2.1–2.2, 2.3–2.5, 2.6, and 2.2–2.6 eV for m -BiVO 4 , t -BiVO 4 , BiV 1.025 O 4+X , Bi 4 V 2 O 11 , Bi 14 V 5 O 33 , Bi 12 V 2 O 23 , and Bi 9 VO 16 , respectively—indicating that they were indirect semiconductors. This study verifies that m -BiVO 4 exhibits the greatest photocatalytic activity and is thus a promising candidate for the use in visible-light–responsive photocatalysts.